650 patients with OIC with a primary endpoint based on a 12-week treatment period.
In addition, one of the pivotal studies has a 6-month double-blind extension. Finally, the 52-week long-term safety study is a randomized, open label study design. This comprehensive Phase 3 program is the only one of its scope and size for the treatment of opioid induced constipation. We are very pleased to report today that AstraZeneca and Nektar anticipate announcing high-level results from the two pivotal studies and the extension study in the fourth quarter of this year. AstraZeneca is also planning a full presentation of the efficacy results at a scientific meeting in 2013. Results from the 1,135 patient long-term open label safety study are anticipated in the first quarter of 2013.
Importantly, AstraZeneca remains on track for mid-2013 global regulatory filings for naloxegol. There are an estimated 100 million chronic pain patients worldwide that are treated with opioids and up to 50% of these long-term pain patients develop constipation. AstraZeneca estimates that there are five key markets that account for over 90% of patients taking opioids for chronic pain – these are the U.S., Canada, France, Germany and the UK. Primary care practitioners and pain management specialists make up the majority of prescribers in these key markets. AstraZeneca, with its global presence, is an ideal development and commercial partner for naloxegol.